Altered expression of SDF-1 and CXCR4 during fracture healing in diabetes mellitus.

PURPOSE: Diabetes mellitus (DM) is known to impair fracture healing. The purpose of this study was to elucidate and compare the gene expression patterns and localization of stromal cell-derived factor 1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) during fracture healing of the femur in rats with and without DM.

METHODS: Closed transverse fractures were created in the femurs of rats equally divided into a DM group and control group; DM was induced by streptozotocin. At post-fracture days five, seven, 11, 14, 21 and 28, total RNA was extracted from the fracture callus and mRNA expression levels of SDF-1 and CXCR4 were measured by real-time polymerase chain reaction. Localization of SDF-1 and CXCR4 proteins at the fracture site was determined by immunohistochemistry at days 21 and 28.

RESULTS: SDF-1 expression was significantly lower in the DM group than in the healthy group on days 21 and 28, and showed a significant difference between days 14 and 21 in the healthy group. There was no significant difference in CXCR4 expression levels between the healthy and DM groups at any time point. On day 21 immunoreactivity of SDF-1 and CXCR4 was detected at the fracture site of the healthy group but no immunoreactivity was observed in the DM group. On day 28, immunoreactivity of SDF-1 and CXCR4 was detected at the fracture site in both groups.

CONCLUSION: Gene expression and localization of SDF-1 and CXCR4 was altered during fracture healing, which may contribute to the impaired fracture healing in DM.